Some conventional separators used in a fuel cell have an uneven shape formed by press working to make a groove-like reactive gas flow path on one surface and a groove-like cooling water flow path on an opposite surface. For example, patent literature 1 teaches a separator having a groove-like flow path extending in a serpentine pattern formed as a fuel gas (hydrogen) flow path on one surface and a groove-like linear flow path formed as a cooling water flow path on an opposite surface. In this separator, the fuel gas flow path has a region where the directions of the flow path change to make each of the fuel gas flow path and the cooling water flow path extend in an orthogonal direction. A shallow groove portion shallower than the other groove portion is formed at a fuel gas flow path groove in this region. As viewed from the cooling water flow path, a groove allowing cooling water to pass through is formed on the rear side of this shallow groove portion. Thus, linear cooling water flow paths parallel to each other are interconnected through this groove to form orthogonal cooling water flow paths. A portion where the direction of the fuel gas flow path or that of the cooling water flow path changes is called a “turn portion.” The other groove portion deeper than the shallow groove portion is called a “deep groove portion.”